The paleoenvironment of Kenyapithecus at Fort Ternan

Abstract

The fossil locality of Fort Ternan, Kenya, preserves the remains of the middle Miocene hominoid Kenyapithecus wickeri, and a reconstruction of the paleoenvironment of this site offers important information about the range of habitats available to this species. Bovids are the most abundant mammals at Fort Ternan. Understanding their habitat preferences provides a basis for reconstructing the paleoenvironment. I present here a study of the morphology of the bovid hind limb that demonstrates a functional linkage between several femoral characters and habitat type as these features relate to locomotion. The majority of bovids living today in savannas are highly cursorial. These species possess a laterally expanded femoral head that limits hind limb movements to the parasagittal plane, and an elliptically shaped patellar groove that provides a large moment arm for the muscles of extension. Forest bovids have a more spherically shaped femoral head that facilitates a high degree of hip abduction and axial rotation. This morphology aids locomotion across the complexly structured substrate of the forest floor. Bovids from broken cover or woodland habitats display intermediate morphologies. A discriminant function analysis that uses the femoral characters to predict habitat type demonstrates a statistically significant separation among a large sample of extant bovids from forest, woodland, and savanna. This study provides a sound basis for interpreting the locomotor adaptations of fossil bovids. The bovids from Fort Ternan display a set of intermediate morphologies most similar to those of extant woodland bovids. The Chinji Formation of Pakistan contains the middle Miocene hominoid Sivapithecus and a parallel analysis of the fossil bovids from these sediments shows that they are most similar to extant forest bovids. This contrast in paleoenvironments suggests that Kenyapithecus and Sivapithecus may have lived in different paleoecological settings. Establishing the relationship between the dietary and locomotor adaptations of these two species and the specific nature of their paleoenvironments has important implications for understanding the course of later hominoid evolution.